Method and apparatus for the separation of manure and sand

ABSTRACT

A method and apparatus for the separation of manure (104) and sand (102) in a sand and manure mixture (100) is described. The apparatus (10) of the first embodiment includes a tank (12) with an upper grate (22), a lower grate (20), an air supply tube (30) and a water supply tube (36). The apparatus (210) of the second embodiment includes a tank (212) having a screened grate (220), an air supply tube (230) and a water supply tube (236). The apparatus (310) of the third embodiment includes a tank (312) having an upper portion (312C) and a conical lower portion (312D) with a grate (320) between the two portions. In operation, all three embodiments essentially operate similarly. The chamber (12F, 212F and 312F) of the tank is filled with water. The mixture is then dumped into the chamber to form the aqueous suspension (106) with the water. In all three embodiment, the flow of air and water if present, agitates the mixture in the suspension which causes the mixture to break down and the sand to separate from the manure. The sand settles on the floor (12B, 212B and 312B) of the tank while the manure remains suspended in the suspension.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a method and apparatus for theseparation of sand and manure from a manure and sand mixture. Inparticular, the present invention relates to a method and apparatus forseparating sand, which is used for bedding animals, such as cows, fromthe manure in order to allow for easy disposal of the manure and reuseof the sand.

The use of sand as a bedding for animals such as cows has becomeincreasingly more widespread. It has been found that the use of sand asa bedding material for cows has several advantages over thetraditionally used chopped straw, sawdust or wood shavings. Some of thebenefits are improved udder health, increased cow comfort, cleaner cows,improved traction and lower cost. One drawback to the use of sand is thesignificant handling and storage problems associated with the resultingmanure and sand mixture. The sand in the mixture obstructs the pumpsnormally used to irrigate the manure suspension onto the surroundingground surface. Further, when the mixture is filled into pits, the sandeventually settles out of the mixture and fills the pit thus, requiringanother pit or excavation of the pit. Either method of disposal iscostly which can negate the benefits associated with the use of sand. Toallow for easy disposal or storage of the mixture, the manure and sandmust be separated. In the past, there was no quick and inexpensive wayof separating the manure from the sand.

(2) Description of the Related Art

The related art has shown an assortment of liquid and solid separationsystems common to waste water treatment operations as well as the dairy,mining and petroleum refining industries. The publication "Handling andStorage Systems For Sand-Laden Dairy Manure From Free Stall Barns", TheProceedings of the Third International Dairy Housing Conference, DairySystems for the 21st Century, 1994 ed. Ray Bucklin, American Society ofAgricultural Engineers by some of the inventors describes the currentmethods of handling sand-laden dairy manure and of separating sand fromsand-laden dairy manure. The paper also describes the characteristics ofa settled sand profile and provides suggestions for long term handlingand storage of sand-laden dairy manure. In addition, the publication,"Analysis of a Batch Aerated Grit Chamber Used to Separate Bedding SandFrom Dairy Manure" 1995 ASAE Annual International Meeting Paper No.95-4705 by the inventors describes several liquid, solid separationtechniques and their effectiveness in separating sand from manure in asand and manure mixture.

Some separation systems such as screening and dissolved air floatationare ineffective for use in separating manure and sand. Screening isineffective due to the similarities in the particle size distributionsof bedding sand and manure. Dissolved air floatation is ineffectivebecause the minute bubbles are unable to float the large, coarse manureparticles to the top of the tank for removal. Some other separationsystems such as sedimentation and the hydrocyclone are more effectivebut have disadvantages. Sedimentation is an effective sand separationtechnique. However, the sand and manure settle out as layers with themanure on top of the sand. The layer of manure on the sand makes removalof the sand difficult without also removing the manure. In addition,dilution rates in excess of 1:1 are required to separate a significantamount of sand from the manure. The separation does not increase fordilution rates greater than 3:1. Hydrocyclones have the potential to beeffective sand separators. However, to be effective, the solid feedconcentration must remain constant which is difficult to achieve withthe manure and sand mixture.

Applications of aeration such as the Pachuca tank and continuous flowaerated grit chambers might also be used to separate sand from manure.However, the prior art does not disclose any such applications usingthese methods for the stated materials. Pachuca tanks are circularvessels with conical bottoms. Air is introduced at the apex of theconical bottom. The purpose of the conical bottom is to redirect settledsolids into the upward flowing fluid so that they may be resuspended.However, because the manure and the sand co-exist in coagulated clumpsof a large size, the effectiveness of this technique is reduced.Continuous flow aerated grit chambers consist of either a circular orrectangular concrete tank with air diffusers positioned above the bottomof the tank. The chamber operates as follows: i) influent waste watercontaining water, organic matter and grit enters the tank; ii) theenergy inputted to the water by a continuous air flow creates hydraulicmovement of the water; iii) grit settles out while organic material iskept in suspension and carried out of the tank; iv) the accumulated gritis then removed immediately from the tank; and v) effluent containingwater and suspended organic matter flows out of the tank. The nature ofthe energy adsorption into the fluid is crucial to effective gritremoval.

The related patent art has also shown various methods and apparatus forseparating different materials having different sizes or weights usingair and water to provide agitation to separate the materials.Illustrative are U.S. Pat. Nos. 2,933,187 to Old et al; 4,324,652 toHack and 4,851,036 to Anthes et al.

Old et al describes an apparatus used for the floatation separation ofparticles, specifically concrete. The apparatus consists of a tankhaving an inclined bottom along which is mounted a combination agitatorand conveyor. Water and air are introduced vertically into the deep endof the tank and the feeding of the material to be separated is downwardinto the tank opposite the air and water. In the separation process, thelightweight material floats and is discharged over the wall of the tankat the deep end. The heavier particles are moved along the tank upwardlytoward the remote end where it is discharged. A removable, verticallyoriented screen extends across the tank, intermediate the ends of thetank and prevents the lightweight material from moving with the heavymaterial toward the shallow end of the tank.

Hack describes a method and apparatus for scrubbing crude oil (bitumen)from tar-sands. The apparatus includes a pair of counter-rotating screwconveyors which tumble the tar-sand so as to rub the grains together andscrub the oil from the sand particles while at the same time moving theprogressively cleaner sand toward the discharge end. An air-aspiratingventuri underneath the sand lying in the bottom of the cell allows forsimultaneously flushing and aerating the sand being tumbled to push theoil particles through the sand and carrying them to the surface.

Anthes et al describes a process and apparatus for separating relativelyfloatable particulate material from a mixture also having relativelynon-floatable, particulate material. The apparatus includes a columnwith at least one baffle to promote turbulence within the column. Air isintroduced into the column below the point of introduction of themixture to be separated. Water is also added to the column. The rates ofintroduction of the mixture, air and water and the number andconfiguration of the baffles must be such as to create a substantialamount of turbulence in the column to keep the relatively floatableparticulate matter at the upper portion of the column.

Also of interest is U.S. Pat. No. 4,617,113 to Christophersen et alwhich shows a floatation separating system. Only of minimal interest areU.S. Pat. Nos. 2,168,942 to McClave; 4,297,208 to Christian and5,368,731 to Pesotini.

There remains a need for an apparatus which easily and quickly separatesthe sand from the manure in a manure and sand mixture and which providesreusable sand and sand free manure.

OBJECTS

It is an object of the present invention to provide an apparatus forseparating sand from manure in a manure and sand mixture which is quickand inexpensive and which provides reusable sand and an easily handlablemanure suspension. Further, it is an object of the present invention toprovide a method for separating manure and sand in a manure and sandmixture which is quick and inexpensive and which provides reusable sandand an easily handlable manure suspension. Still further, it is anobject of the present invention to provide an apparatus which uses airand water to agitate an aqueous suspension containing the manure andsand mixture in order to separate sand from manure. Further still, it isan object of the present invention to provide an apparatus which uses agrate to help disperse the manure and sand mixture. These and otherobjects will become increasingly apparent by reference to the followingdrawings and the description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the separation apparatus 10 of the firstembodiment.

FIG. 2 is a front view of the apparatus 10 of FIG. 1.

FIG. 3 is a cross-sectional view of the apparatus 10 of FIG. 2 along theline 3--3 showing the upper grate 22, the lower grate 20, the air supplytube 30, the water supply tube 36 and the baffle system 24.

FIG. 4 is a top view of the apparatus 10 of FIG. 3 along the line 4--4showing the upper grate 22 and the baffle system 24.

FIG. 5 is a cross-sectional view of the apparatus 10 of FIG. 3 along theline 5--5 showing the lower grate 20.

FIG. 6 is a cross-sectional view of the apparatus 10 of FIG. 3 along theline 6--6 showing the air and water tubes 30 and 36 mounted in thechamber 12F.

FIG. 7 is a partial, perspective view of the apparatus 10 of the firstembodiment showing the screw conveyor 48.

FIG. 8 is a cross-sectional view of the apparatus 10 of FIG. 7 along theline 8--8 showing the screw conveyor 48 spaced below the water and airtubes 36 and 30.

FIG. 9 is a front view of the apparatus 210 of the second embodimentwith cutout portions showing the air tube 230 and the water tube 236.

FIG. 10 is a cross-sectional side view of the apparatus 210 of FIG. 9along the line 10--10 showing the screened grate 220.

FIG. 11 is a cross-sectional top view of the apparatus 210 of FIG. 10along the line 11--11 showing the screened grate 220.

FIG. 12 is a cross-sectional top view of the apparatus 210 of FIG. 10along the line 12--12 showing the air tube 230 and the water tube 236,mounted on the chamber 212F.

FIG. 13 is a cross-sectional front view of the apparatus 310 of thethird embodiment showing the grate 320 and the air inlet 330 in thebottom of the chamber 312F.

FIG. 14 is a cross-sectional top view of the apparatus 310 of FIG. 13along the line 14--14 showing the grate 320.

FIG. 15 is a view of the baffle system 24 of the first embodiment havingthe floatation blocks 27 on the baffle plates 25.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention relates to an apparatus for separating manure fromsand in a manure and sand mixture wherein the sand has been used as abedding for an animal which produces the manure, which comprises: a tankhaving a top portion spaced above a bottom portion for holding anaqueous suspension into which the manure and sand mixture is fed; aperforate means mounted in the tank between the top and bottom portionof the tank such as to prevent the mixture fed into the top portion ofthe tank from falling to the bottom portion of the tank; a fluid supplymeans mounted on the tank for introducing fluid into the tank whichagitates the aqueous suspension and separates the manure and the sandfrom the manure and sand mixture such that the sand passes through theperforate means and the manure is dispersed in the suspension; sandremoval means mounted at the lower portion of the tank for removing thesand from the tank; and manure removal means provided on the tank forremoving the manure dispersed in the aqueous suspension from the tankafter the sand has been separated from the manure.

Further, the present invention relates to a method for separating manurefrom sand in a manure and sand mixture wherein the sand has been used asa bedding for an animal which produces the manure, which comprises: (i)introducing the manure and sand mixture into an apparatus whichcomprises: a tank having a top portion spaced above a bottom portion forholding an aqueous suspension into which the manure and sand mixture isfed; a perforate means mounted in the tank between the top and bottomportion of the tank such as to prevent the mixture fed into the topportion of the tank from falling to the bottom portion of the tank; afluid supply means mounted on the tank for introducing fluid into thetank which agitates the aqueous suspension and separates the manure andthe sand from the manure and sand mixture such that the sand passesthrough the perforate means and the manure is dispersed in thesuspension; sand removal means mounted at the lower portion of the tankfor removing the sand from the tank; and manure removal means providedon the tank for removing the manure dispersed in the aqueous suspensionfrom the tank after the sand has been separated from the manure; (ii)activating the fluid supply means until most of the sand is in thebottom portion of the tank; and (iii) removing the manure dispersed inthe aqueous suspension from the tank through the manure removal meansand removing the sand from the tank through the sand removal means.

FIGS. 1 to 6 show the manure and sand separation apparatus 10 of thefirst embodiment. The apparatus 10 allows for quick and inexpensiveseparation of the sand 102 from the manure 104 in the manure and sandmixture 100. The first embodiment of the apparatus 10 includes a tank12, an upper grate 22, a lower grate 20, an air supply tube 30, a watersupply tube 36 and a baffle system 24.

The tank 12 preferably has an open top 12A and a sloped floor 12B with afront wall 12C, a back wall 12D and two (2) sidewalls 12E spacedtherebetween which form a chamber 12F. The floor 12B of the tank 12 ispreferably sloped upward from the front wall 12C to the back wall 12D atan angle of between about 25° and 65° such that the back wall 12D of thetank 12 is shorter than the front wall 12C of the tank 12. The slope ofthe floor 12B allows for the build up of the sand 102 adjacent the door14 and the front wall 12C of the tank 12 for easier removal of the sand102. The front wall 12C of the tank 12 is preferably provided with adoor 14 adjacent the floor 12B of the tank 12. The door 14 has an outlet16 with a valve 18. The valve 18 enables the outlet 16 to be used toremove the aqueous suspension (slurry) 106 containing the manure 104after the sand 102 has been removed. The outlet 16 preferably has acircular cross-section with at least a 2.0 inch (5.1 cm) diameter suchthat the aqueous suspension 106 does not clog the outlet 16. The door 14is sealably mounted over an opening in the front wall 12C of the tank 12such that the aqueous suspension 106 in the chamber 12F does not leakfrom the chamber 12F around the union of the door 14 and the front wall12C. The door 14 is preferably removably mounted over the opening of thefront wall 12C such that after the aqueous suspension 106 containing themanure 104 is removed from the chamber 12F, the door 14 is removed toallow removal of the sand 102 from the chamber 12F. The door 14 may alsobe attached to the front wall 12C of the tank 12 by a hinge (not shown)which allows for easy opening and closing of the door 14. In the firstembodiment, the tank 12 is able to handle the sand and manure mixture100 associated with 10 cows per day with the mixture 100 added as twobatches a day. The tank 12 has an essentially rectangular cross-sectionwith a height of 84.0 inches (213.4 cm) from the floor 12B to the opentop 12A of the tank 12, a width along the sidewalls 12E of 50.0 inches(127.0 cm) and a length across the front and back walls 12C and 12D of28.0 inches (71.1 cm). The chamber 12F of the tank 12 is able to hold390 gallons of the aqueous suspension 106. A fluid indicator 54 ispreferably provided on the outside of the tank 12 to allow the user tomonitor the level of the suspension 106 in the tank 12.

A lower grate 20 is provided within the chamber 12F of the tank 12(FIGS. 3 and 5). The grate 20 preferably extends across the entire widthand length of the chamber 12F between the open top 12A and the floor 12Bof the tank 12. Preferably, the grate 20 is adjacent the intersection ofthe back wall 12D and the sloped floor 12B and extends perpendicular tothe walls 12C, 12D and 12E of the tank 12.

An upper grate 22 is positioned in the chamber 12F adjacent the open top12A of the tank 12 (FIG. 3). The upper grate 22 is preferably of such asize as to span the entire length of the chamber 12F but not such as tonot span across the entire width of the chamber 12F. The upper grate 22preferably has a width of 14 inches (36 cm). The upper grate 22 ispositioned slightly closer to the front wall 12C of the tank 12 than theback wall 12D such that the upper grate 22 is spaced directly above theair supply tube 30 (to be described in detail hereinafter). The uppergrate 22 is provided with sides 22A which extend upward toward the top12A of the tank 12 along the length of the upper grate 22. The sides 22Ahold the manure and sand mixture 100 on the upper grate 22. The grates20 or 22 preferably have mesh openings about 0.50 inch (1.27 cm) or haveparallel spaced bars (not shown) about 1.0 inch (2.54 cm) apart. Thesize of the mesh openings or spacing of the bars of the grates 20 and 22will depend upon the consistency and composition of the manure and sandmixture 100.

The chamber 12F is provided with a baffle system 24 which includesplates 25 which extend along the front wall 12C and the back wall 12D ofthe tank 12 (FIGS. 3 and 15) and floatation tubes 26 which connect theends of the plates 25 together and which extend along the sides 12 ofthe tank 12. The tubes 26 hold the plates 25 at approximately a 45°angle. The floatation tubes 26 are preferably hollow tubes constructedof a durable, lightweight material such as PVC which are sealed at bothends with air trapped in the tubes 26. The trapped air allows the bafflesystem 24 to float at the top of the aqueous suspension 106. In analternate embodiment, the baffle plates 25 of the system 24 havefloatation blocks 27 such as polystyrene blocks mounted to the top sideof the plates 25 which allow the baffle system 24 to float at the top ofthe aqueous suspension 106 in the tank 12 (FIG. 3). The plates 25 areslidably mounted on shafts 28 which extend upward from the lower grate20 through each end of the plates 25. In either embodiment, preferablythe baffle system 24 is able to move between the lower grate 20 and theupper grate 22. The exact height of the baffle system 24 willnecessarily depend upon the level of the aqueous suspension 106 in thechamber 12F.

An air supply tube 30 and a water supply tube 36 are provided adjacentthe floor 12B of the tank 12 (FIG. 3). The air supply tube 30 ispreferably positioned adjacent the front wall 12C of the tank 12 abovethe floor 12B of the tank 12. The water supply tube 36 preferablyextends across the length of the tank 12 between the sidewalls 12E. Inthe first embodiment, the air tube 30 is held in place on one of thesidewalls 12E of the tank 12 by a bracket 32 and extends outward to andthrough an opening in the other sidewall 12E of the tank 12. A sealingring 34 is mounted around the tube 36 at the opening in the sidewall 12Eand prevents the aqueous suspension 106 in the chamber 12F from leakingthrough the opening (FIG. 2). The air tube 30 is preferably able to beeasily removed from the tank 12 to allow repair of the tube 30. Theorifices 30A are provided opposite the floor 12B and allow for uniformdispersion of the air across the tank 12. The direction in which the airtravels upward through the water in the chamber 12F is in part due tothe current in the tank 12 created by the previous air bubbles. Thecurrent causes the air to move upward and across the tank. The directionof travel of the air is also influenced by the baffle system 24. Theplacement of the orifices 30A may be varied. In the first embodiment,the tube 30 has a diameter of 0.75 inches (1.91 cm) and the orifices 30Ahave a diameter of 0.063 inches (0.16 cm). The air tube 30 is connectedto an air valve 38 on the outside of the tank 12. The air valve 38 isprovided with a meter (not shown) to allow the user to determine theamount of air being injected into the tank 12. The air in the air tube30 preferably has a pressure sufficient to overcome static and dynamicpressure losses and to thus provide equivalent flow through each orifice30A of the air tube 30. In the first embodiment, the pressure ispreferably 10 PSI. The air supply for the air tube 30 is preferably acompressor (not shown) however, any type of air supply may be used. Inthe first embodiment, the air tube 30 provides about 8 CFM into the tank12.

The water tube 36 is preferably spaced apart from the air tube 30 towardthe back wall 12D of the tank 12. The water tube 36 is preferablymounted similarly to the air tube 30 between the sidewalls 12E of thetank 12. The water tube 36 also has orifices 36A however, the orifices36A of the water tube 36 are preferably spaced in the sides of the tube36 such that the water exiting the tube 36 is tangent to the slopedfloor 12B of the tank 12 (FIG. 3). In the first embodiment, the watertube 36 has a diameter of 0.75 inches (1.91 cm) and provides about 5gal/min of water into the tank 12. The water tube 36 is connected to awater valve 42 and meter (not shown) to allow the user to vary theamount of water entering the tank 12. The water supply is of any typesuch as a direct hook up to the water supply for a building (not shown)housing the tank 12 or to a pond (not shown).

In an alternate embodiment as shown in FIGS. 7 and 8, the slope of thetank 12 is provided with a screw conveyor 48. The screw conveyor 48 ispreferably mounted adjacent the front wall 12C of the tank 12.Preferably, the screw conveyor 48 does not extend upward such a distanceas to interfere with the water and air tubes 36 and 30. The screwconveyor 48 extends from one sidewall 12E of the tank 12 and through theother sidewall 12E of the tank 12. In the first embodiment, the screwconveyor 48 extends out the sidewall 12E opposite to the sidewall 12Ethrough which the air and water tubes 30 and 36 extend. As the screwconveyor 48 extends beyond the tank 12, the conveyor 48 is preferablysurrounded by a cover 50. The conveyor motor 52 is mounted at the end ofthe cover 50 opposite the sidewall 12E. The bottom of the cover 50 hasan outlet 50A between the sidewall 12E and the conveyor motor 52 whichallows the sand 102 moved out of the tank 12 by the conveyor 48 to beremoved from the conveyor 48. The cover 50 for the conveyor 48preferably prevents leakage of the aqueous suspension 106 and the sand102 out of the tank 12 except through the outlet 50A. In an alternateembodiment (not shown), the conveyor 48 is located below the floor 12Bof the tank 12 such that the conveyor 48 is the lowest portion of thetank 12. The screw conveyor 48 may also be angled along the floor 12B ofthe tank 12 such that sand 102 is collected along the entire width ofthe tank 12. The sand 102 is then carried upward out the back wall 12Dof the tank 12. The screw conveyor 48 is preferably similar to screwconveyors well known in the art.

In a second embodiment, as shown in FIGS. 9 to 12, the tank 212 issimilar in shape to the tank 12 of the first embodiment. The floor 212Bis preferably sloped at a 45° angle. In the second embodiment, theaqueous suspension outlet 216 is provided in the back wall 212D of thetank 212 adjacent the floor 212B. The tank 212 has an adjustablescreened grate 220 (FIG. 11). The screened grate 220 includes a screen220A and a grate 220B which are preferably mounted together. Thescreened grate 220 is mounted in the chamber 212F such that the screen220A is spaced above the grate 220B below the open top 212A of the tank212. The screened grate 220 is preferably mounted by chains 222 orcables which are connected at one end to the sidewalls 212E of the tank212 adjacent the open top 212A and at the other end to the screenedgrate 220 (FIG. 10). The chains 222 allow the height of the screenedgrate 220 to be adjusted such as to vary the distance between thescreened grate 220 and the water and air supply tubes 236 and 230. Thescreened grate 220 is preferably the same shape as the cross-section ofthe tank 212. The screened grate 220 is preferably of such a size suchas to easily move up and down within the chamber 212F and to be closelyadjacent to all the walls 212C, 212D and 212E of the tank 212 to preventthe mixture 100 from passing between the screened grate 220 and thewalls 212C, 212D and 212E of the tank 212. The screen 220A preferablyhas mesh openings of approximately 0.50 inch (1.27 cm). The grate 220Bpreferably has bars spaced approximately about 1.0 inch (2.54 cm) apart.

In the second embodiment, the air and water tubes 230 and 236 aremounted parallel to the sloped floor 212B of the tank 212 with the airtube 230 spaced in front of and below the water tube 236 adjacent thedoor 14 (FIGS. 9 and 10). The water and air tubes 236 and 230 extendthrough opposite sidewalls 212E and the valves 238 and 242 are mountedadjacent the opposite sidewalls 212E of the tank 212. The positioning ofthe valves 238 and 242 and the mounting of the air and water tubes 230and 236 through the sidewalls 212E depend upon the particular design ofthe tank 212. The size of the air and water tubes 230 and 236 arepreferably similar to those of the first embodiment and preferably thepressure of the air and water entering the tank 212 are similar to thoseof the first embodiment. The size and position of the orifices 236A and230A in the water and air tubes 236 and 230 are similar to the firstembodiment with the air orifices 230A in the top of the air tube 230 andthe water orifices 236A in the side of the water tube 236 aimed tangentto the floor 212B.

FIGS. 13 and 14 show the apparatus 310 of the third embodiment of thepresent invention. As shown in FIG. 12, the tank 312 of the thirdembodiment has a cylindrical upper portion 312C with a conical lowerportion 312D. The air inlet 330 is provided in the apex of the conicallower portion 312D of the tank 312. The air inlet 330 has a singleorifice which forces air upward toward the top 312A of the tank 312. Thetank 312 is preferably similar to the Pachuca tank of the related art.However, unlike the Pachuca tank, the tank 312 of the third embodimentis provided with a grate 320 mounted in the upper portion 312C of thetank 312 and extending across the entire cross section of the tank 312.The grate 320 acts to slow the descent of the mixture 100 to the bottomof the tank 312. This added holdup time allows sufficient contactbetween the mixture 100 and the moving, aqueous suspension 106 to erodethe mixture 100 into small particles. The mixture 100 then enters thelower portion 312D of the tank 312 in a dispersed form. Dispersion ofthe particles in the mixture 100 allows the flow of air from the airinlet 330 to effectively act on the mixture 100 to separate the sand 102from the manure 104 in the mixture 100. The grate 320 is preferablysimilar to the lower grate 20 of the first embodiment. A door (notshown) may be provided on the lower portion 312D of the tank 312 forremoval of the sand 102. An outlet (not shown) is also provided in thelower portion 312D of the tank 312 to allow for removal Of the aqueoussuspension 106.

In all three of the embodiments, the tank 12, 212 and 312 is preferablyconstructed of steel however, any suitable material could be used. Thegrates 20, 22, 220 and 320 of all three embodiments are preferablyconstructed of steel however, other materials such as nylon or plasticcould also be used.

IN USE

In general, all three embodiments operate similarly and use a batchoperation. Preferably, water is first added to the tank 12, 212 or 312to the level of the lower grate 20 in the first embodiment or to thescreened grate 220 or grate 320 in the second and third embodiments. Theair flow is then activated to establish a stable circulation pattern inthe added water. The air flow rate is pre-adjusted such that theestablished currents in the suspension 106 allow for deposition of thesand 102 to the bottom of the tank 12, 212 or 312, but do not allow fordeposition of manure 104 contained in the suspension 106. The positionof the air tube 30 or 230 or air inlet 330, the direction of air flow,the position of the baffle system 24 (if present) and the geometry ofthe tank 12, 212 or 312 all affect the currents established in thewater. Next, a batch of the manure and sand mixture 100 is fed throughthe open top 12A, 212A or 312A of the tank 12, 212 or 312 into thechamber 12F, 212F or 312F. The mixture 100 may be provided into the opentop 12A, 212A or 312A in several ways. The mixture 100 may be dumpedinto the open top 12A, 212A or 312A using a front end loader 400 to movethe mixture 100 into a bin 13 situated over the top 12A, 212A or 312A ofthe tank 12 (FIG. 1). The mixture 100 may also be slowly fed into thetank 12, 312 or 312 by means of a conveyor (not shown) or a pump (notshown). The amount of mixture 100 able to be handled by the apparatus10, 210 or 310 will depend upon the size of the tank 12, 212 or 312.

In the first embodiment, the mixture 100 is fed into the open top 12A ofthe tank 12 onto the upper grate 22 (FIG. 1). The sides 22A of the grate22 allow the mixture 100 to be piled onto the upper grate 22 without themixture 100 falling off the grate 22. The upper grate 22 preventsclogging of the apparatus 20 by slowly metering the mixture 100 into thechamber 12F during the batch process. In the first embodiment, a batchof mixture 100 is approximately about 440 lbs. which represents about 99lbs. of sand 102 and 341 lbs. of manure 104. The batch preferablyrepresents one half of the amount of mixture 100 resulting from the useof sand 102 as bedding for 10 cows for one (1) day. Preferably, twobatches of mixture 100 are run through the apparatus 10, 210 or 310 perday.

In the second embodiment, the mixture 100 is dropped directly onto thescreened grate 220. The screened grate 220 prevents the mixture 100 fromdropping directly to the bottom 212B of the tank 212. The smaller meshof the screen 220A in the second embodiment prevents the clumps orparticles of the mixture 100 from passing through the screened grate 220until the particles are smaller than the mesh of the screen 220A.

In the third embodiment, the mixture 100 is dropped on the grate 320which prevents the manure and sand mixture 100 from immediately settlingin the lower portion 312D of the tank 312 which prevents clogging of theair inlet 330 and enables the mixture 100 to be acted on by the flow ofair from the air inlet 330.

The dispersed mixture 100 then becomes a portion of the aqueoussuspension 106. The dispersed particles of mixture 100 are aggressivelymixed in the established current wherein the sand 102 becomes separatedfrom the manure 104. More water is then added to the tank 12, 212 or312. As the water level rises, aggressive erosion of the sand and manuremixture 100 remaining on the grate 20, 220 or 320 begins.

In the first and second embodiments, the air and water continue to acton the layer of sand 102 forming on the floor 12B or 212B of the tank 12or 212. The placement of the air and water tubes 30, 230, 36 and 236enables the tubes 30, 230, 36 and 236 to be within the layer of sand102. The air and water act in concert to create rapidly opening andclosing channels within the layer of sand 102. Preferably, the aircreates an open channel and the fresh water collapses the air generatedchannel. This has two effects. First, the opening and closing of thechannels by the air and water allow free paths for any manure 104 whichhave become entrapped in the layer of sand 102 and allow the manure 104to be lifted by the nature of buoyant forces away from the layer of sand102. Second, the air and water movement allows for erosion andsubsequent movement of the sand 102 towards the floor 12B or 212B of thetank 12 or 212 for removal. The cleaning of the manure 104 from thesettled sand 102 and the movement of the sand 102 towards the floor 12Bor 212B of the tank 12 and 212 are unexpected benefits of the apparatus10 and 210. The slow addition of fresh water below the layer of sand 102in the tank 12 or 212 also acts to cleanse the sand 102 of organicmaterial as well as to dilute any organics in suspension located betweenthe particles of sand 102. The rising, circulated water and the grate 20and 220 act in concert to allow the slow erosion and dispersement of themixture 100 into the aqueous suspension 106.

In the third embodiment, the air inlet 330 acts similarly to the airtubes 30 and 230 of the first and second embodiments and operates toseparate the sand 102 from the manure 104 in the mixture 100 such thatthe sand 102 settles in the lower portion 312D of the tank 312 while themanure 104 remains suspended as part of the aqueous suspension 106.

The separation process is initially completed when the tank 12, 212 or312 is completely filled with water. In the first embodiment, it takesapproximately 15 minutes for the water level in the tank 12 to reach thefull level which is approximately about 4.0 inches (10.2 cm) from thetop 12A of the tank 12 or level with the tops of the sides 22A of theupper grate 22. At this point, the water is shut off. The baffle system24 preferably floats at the top of the aqueous suspension 106, levelwith the upper grate 22 (FIG. 3). Air may be continued to be added for atime after the tank 12 is full to keep the manure 104 from settling ontothe layer of sand 102 and may be used to better cleanse the sand 102 foraesthetic reasons. In the first embodiment, the air tube 30 is left "on"for about another 10 minutes and continues to aerate the aqueoussuspension 106 to allow the sand 102 to settle out of the suspension106.

In an alternative mode, fresh water may be continued to be added for aslong as desired, with continuous overflow of aqueous suspension 106containing the manure 104 from a point near the top 12A, 212A or 312A ofthe tank 12, 212 or 312. This will produce very clean sand 102 and verydirty or manure 104 rich aqueous suspension 106.

Once the sand 102 has settled out of the suspension 106, the separationof the mixture 100 is complete. The aqueous suspension 106 containingthe manure 104 is then removed from the tank 12, 212 or 312 preferably,through the outlet 16 or 216. The sand 102 is either removed manuallysuch as through the door 14 or 214 located adjacent to the floor 12B or212B of the tank 12 or 212. The aqueous suspension 106 which containsthe manure 104, may then be used to fertilize and irrigate usingconventional, well known methods and apparatuses for spreadingfertilizer. In the first embodiment, for a batch containing 440 lbs. ofthe manure and sand mixture 100, approximately 95 lbs. of sand 102 areremoved. The sand 102 which is removed from the tank 12, 212 or 312preferably contains less than 2% organic matter.

In the alternative embodiment having the conveyor 48, once the sand 102has settled out of aqueous suspension 106, the sand 102 is removed bythe conveyor 48 while the aqueous suspension 106 containing the manure104 remains in the tank 12. Once the sand 102 is removed, the air isshut off and the manure 104 is allowed to settle out of the aqueoussuspension 106. A thickened manure suspension (slurry) may then beremoved via the conveyor 48 and a very dilute aqueous suspension 106removed by the outlet 16.

It is intended that the foregoing description be only illustrative ofthe present invention and that the present invention be limited only bythe hereinafter appended claims.

We claim:
 1. An apparatus for separating manure from sand in a manureand sand mixture wherein the sand has been used as a bedding for ananimal which produces the manure, which comprises:(a) a tank having atop portion spaced above a bottom portion for holding an aqueoussuspension into which the manure and sand mixture is fed; (b) aperforate means mounted in the tank between the top and bottom portionof the tank such as to prevent the mixture fed into the top portion ofthe tank from rapidly falling to the bottom portion of the tank; (c) afluid supply means mounted on the tank for introducing fluid into thetank which agitates the aqueous suspension and separates the manure andthe sand from the manure and sand mixture such that the sand passesthrough the perforate means and the manure is dispersed in thesuspension; (d) sand removal means mounted at the lower portion of thetank for removing the sand from the tank; and (e) manure removal meansprovided on the tank for removing the manure dispersed in the aqueoussuspension from the tank after the sand has been separated from themanure.
 2. The apparatus of claim 1 wherein the lower portion of thetank has a sloped floor.
 3. The apparatus of claim 2 wherein the slopedfloor has a slope of between 25° and 65°.
 4. The apparatus of claim 2wherein the fluid supply means is mounted below the perforate meansadjacent a lowest portion of the floor of the tank.
 5. The apparatus ofclaim 2 wherein the fluid supply means introduces the fluid in adirection tangent to the floor of the tank.
 6. The apparatus of claim 5wherein the fluid is water.
 7. The apparatus of claim 1 wherein thefluid supply means is a pair of conduits extending across a length ofthe tank parallel to the floor of the tank.
 8. The apparatus of claim 1wherein the perforate means includes a screen mounted above a grate asthe perforate means.
 9. The apparatus of claim 8 wherein the screen hasa mesh of about 0.25 to 0.75 inch (0.64 to 1.91 cm) and the grate hasbars spaced about 1.00 inch (2.54 cm) apart.
 10. The apparatus of claim1 wherein a pair of baffles are movably positioned adjacent oppositesides of the top portion of the tank at a fluid level of the aqueoussuspension which acts to promote a current in the aqueous suspension inthe tank as a result of the introduction of the fluid.
 11. The apparatusof claim 1 wherein the sand removal means is a conveyor means whichremoves the sand from the lower portion of the tank.
 12. The apparatusof claim 11 wherein the conveyor means is a screw conveyor.
 13. Theapparatus of claim 1 wherein the fluid supply means includes an airsupply means and a water supply means.
 14. The apparatus of claim 1wherein the fluid is air.
 15. The apparatus of claim 10 wherein thebaffles include angled plates connected together by hollow tubes havingair trapped inside.
 16. A method for separating manure from sand in amanure and sand mixture wherein the sand has been used as a bedding foran animal which produces the manure, which comprises:(a) introducing themanure and sand mixture into an apparatus which comprises: a tank havinga top portion spaced above a bottom portion for holding an aqueoussuspension into which the manure and sand mixture is fed; a perforatemeans mounted in the tank between the top and bottom portion of the tanksuch as to prevent the mixture fed into the top portion of the tank fromfalling rapidly to the bottom portion of the tank; a fluid supply meansmounted on the tank for introducing fluid into the tank which agitatesthe aqueous suspension and separates the manure and the sand from themanure and sand mixture such that the sand passes through the perforatemeans and the manure is dispersed in the aqueous suspension; sandremoval means mounted at the lower portion of the tank for removing thesand from the tank; and manure removal means provided on the tank forremoving the manure dispersed in the aqueous suspension from the tankafter the sand has been separated from the manure; (b) activating thefluid supply means until most of the sand is in the bottom portion ofthe tank; and (c) removing the manure dispersed in the aqueoussuspension from the tank through the manure removal means and removingthe sand from the tank through the sand removal means.
 17. The method ofclaim 16 wherein the fluid supply means is activated before the manureand sand mixture is introduced into the tank.
 18. The method of claim 16wherein the fluid supply means is deactivated before the sand and themanure liquid suspension are removed.
 19. The method of claim 16 whereinthe manure in the aqueous suspension which is removed and is applied tosoil as fertilizer.
 20. The method of claim 16 wherein the sand which isremoved is reused as animal bedding.
 21. The method of claim 16 whereinthe animal is a bovine.